This invention relates to percussion rock drilling equipment and more particularly to rock drill bits for percussion drills.
Drilling through earth rock is generally a rather expensive procedure because of the initial capital costs and the rather large expense required to maintain the equipment in operation. One of the major costs relates to the frequent replacement of drill bits. A rock drill bit generally has a rather short life depending upon various factors including the diameter of the hole. Applicant has found that most commercially available rock drill bits for drilling 6-10 inch holes generally break from fatigue within 500 feet of rock drilling operation. The casualty rate for single rock drilling bits capable of drilling larger holes of 10-18 inches is even greater. As stated in Kurt et al U.S. Pat. No. 3,144,084 granted Aug. 11, 1964, it has not been economically practical to use single rock drilling bits for drilling holes much larger than 9 inches in diameter. The Kurt et al patent suggests that gang drills with multiple bits be used for drilling holes greater than 9 inches.
The problem is even more drastically compounded when a single enlarged anvil bit is utilized for forming or drilling holes having diameters between 9 and 16 inches.
FIG. 1 illustrates a conventional anvil bit for drilling holes of 8-10 inches in diameter that has failed under fatigue. Fracture locations A and B are indicated at the locations where the fatigue fractures normally occur causing bit failure. FIG. 2 illustrates a conventional large diameter anvil bit that has been utilized for drilling rock holes with diameters between 10 and 16 inches. Fracture locations C and D indicate locations where such large diameter art anvil bits normally fail from fatigue.
One of the principal objects of this invention is to provide a new anvil bit that is much more fatigue resistant giving it a considerably longer life.
An additional object of this invention is to provide a new anvil bit design which enables a single anvil bit to be utilized for drilling larger diameter holes than previously.
A further object of this invention is to provide a new anvil bit design which considerably reduces the replacement costs should the anvil bit fail.
An additional object of this invention is to provide an anvil bit for a percussion rock drill that is less expensive to manufacture, yet has a longer life than previous anvil bits.
These and other objects and advantages of this invention will become apparent upon reading the following detailed description of a preferred embodiment.